How to rid of "seams" from texture?
I suggest using the image options in the UV Editor to better unwrap your mesh first. Try the Color Grid to see how the image flows on your mesh object first before trying to go to Substance Painter to make the texture paint, as Substance won't correct a bad UV Unwrap. Look into unwrapping each part separately using 'Follow Active Quads' to get a better alignment and flow on the mesh.